The present invention relates to a multilayered arrangement for electro-optical devices, particularly an arrangement having a conductive organic layer on a transparent electrode on a substrate, where the substrate is preferably a transparent polymer.
Display devices having cathode ray tubes (CRTs) which can be used for televisions or personal computers (PCs), and the like, have large-area screens. However, since a screen coated with a luminescent material must be arranged at a pre-determined distance from the electron gun in these display devices, a problem exists in that the total volume of such display devices is too large. Thus, a CRT device of this type cannot be used for electronic equipment having small dimensions and low power consumption, such as for a television set which can be hung on walls, for portable television sets and notebook computers, etc. For devices having small dimensions and low power consumption, flat panel display devices, such as liquid-crystal display devices (LCDs, for example TN, STN and DSTN displays, ferroelectric displays and polymer dispersed LC arrangements (PDLCs)), plasma display panels (PDPs), organic electroluminescent displays (OELDs), electrophosphorescent displays (OELDs with phosphorescent emitters) and vacuum fluorescent displays (VFDs), or electrochromic displays (ECDs) and electronic paper or electronic ink have been developed. Of these flat panel display devices, the LCDs have been the most researched recently, in spite of various disadvantages, since they have high image quality and low power consumption. There are two types of LCD: LCDs having a passive matrix and LCDs having an active matrix (AMLCD, active matrix LCD). Of these LCDs, the AMLCD is the LCD type which has been most used recently, since in these, each pixel can be addressed independently by a switching element, enabling a high contrast ratio and high resolution to be achieved since the interference caused by adjacent pixels is reduced.
In general, liquid crystals are easily affected by external influences, such as an electric field, a magnetic field, tension, pressure, and the like. Owing to these properties, liquid crystals are used as light diaphragms or even as display devices.
In order to utilize these properties of liquid crystals, they can, if necessary, be moved under the influence of the environment. For uniform alignment of liquid crystals, a homogeneous and smooth underlayer (substrate), inter alia, is vital in addition to the actual alignment layer (rubbed polyimide). The multilayered structure of various LCD types is described, for example, in “Displays: Einführung in die Technik aktiver und passiver Anzeigen” (Displays: Introduction to the Technology of Active and Passive Displays), Peter M. Knoll, Hüthig Verlag Heidelberg, 1986.
The interest in flexible displays and display devices has recently been increasing. The transparent substrates used here are polymer films, such as polycarbonate or other transparent polymers. These substrates are provided with a conductive layer, preferably indium-tin oxide (ITO). However, a disadvantage here is the excessive roughness of the conductive layer, which can result in short-circuits during operation and high reject rates during production. For manufacturing reasons, conventional inorganic conductive layers always have greater roughness on plastic substrates than on glass. Furthermore, inorganic conductive layers such as ITO are brittle, with the consequence that cracks occur on flexible substrates owing to the different coefficients of expansion or extensibility and toughness, which may result in interruption of the electrical conductivity. This arises in particular during storage and/or handling of coiled substrates, such as, for example, ITO-PET for roll to roll processes.
The object of the invention was therefore to develop novel layer arrangements which do not exhibit the said disadvantages.